The present invention relates to perfluoropolyethers having fluorinated epoxy groups positioned along their chain, obtained by starting from a mixture of a perfluoroolefin and a perfluorodiene.
It is known that in low-temperature photooxidation of perfluoroolefins (from -30.degree. C. to -60.degree. C.) with molecular oxygen and in the presence of U.V. light, the primary reaction product is a perfluoropolyether consisting of sequences of oxyperfluoroalkylene units and containing peroxy groups in a variable amount as a function of the reaction conditions. The removal of the peroxy groups in order to obtain stable perfluoropolyethers is carried out by thermal way, by a long heating at a high temperature. See U.S. Pat. Nos. 3,715,378 and 3,665,041.
It is known from U.S. Pat. No. 3,451,907 that perfluorobutadiene, either alone or as a mixture with a perfluoroolefin, when subjected to oxidation with molecular oxygen, at low temperature, in the liquid phase and in the presence of U.V. light, yields photooxidation polymeric products, characterized by the contemporaneous presence of peroxy groups, of fluorinated epoxy groups: ##STR1## of acidic --COF groups. The complete elimination of the peroxy groups from the photoxidation products, carried out by thermal way according to the known art, consisting in heating at temperatures of at least 200.degree. C. for very long times (some hours) causes, necessarily, the contemporaneous decomposition of the epoxy groups, which are mostly converted into acidic --COF groups.